WOX family transcriptional regulators modulate cytokinin homeostasis during leaf blade development in Medicago truncatula and Nicotiana sylvestris

Abstract

The plant-specific family of WUSCHEL (WUS)-related homeobox (WOX) transcription factors is key regulators of embryogenesis, meristem maintenance, and lateral organ development in flowering plants. The modern/WUS clade transcriptional repressor STENOFOLIA/LAMINA1(LAM1), and the intermediate/WOX9 clade transcriptional activator MtWOX9/NsWOX9 antagonistically regulate leaf blade expansion, but the molecular mechanism is unknown. Using transcriptome profiling and biochemical methods, we determined that NsCKX3 is the common target of LAM1 and NsWOX9 in Nicotiana sylvestris. LAM1 and NsWOX9 directly recognize and bind to the same cis-elements in the NsCKX3 promoter to repress and activate its expression, respectively, thus controlling the levels of active cytokinins in vivo. Disruption of NsCKX3 in the lam1 background yielded a phenotype similar to the knockdown of NsWOX9 in lam1, while overexpressing NsCKX3 resulted in narrower and shorter lam1 leaf blades reminiscent of NsWOX9 overexpression in the lam1 mutant. Moreover, we established that LAM1 physically interacts with NsWOX9, and this interaction is required to regulate NsCKX3 transcription. Taken together, our results indicate that repressor and activator WOX members oppositely regulate a common downstream target to function in leaf blade outgrowth, offering a novel insight into the role of local cytokinins in balancing cell proliferation and differentiation during lateral organ development.

Auxin biosynthesis gene FveYUC4 is critical for leaf and flower morphogenesis in woodland strawberry

“…These WOX genes can interact with the auxin pathway by promoting YUC gene expression (Zhang et al., 2020). In contrast, WOX9 acts as a negative regulator of leaf expansion (Lin et al., 2013; Wolabu et al., 2021), which can activate the expression of CKX3 , which encodes the catabolic enzyme of cytokinin (Wang et al., 2022). Gene expression analysis revealed that FveWOX9 and FveCKX3 were significantly upregulated in the yuc4 leaves, suggesting that they may play a role in leaf expansion in strawberry.…”

“…Several homologs of the known leaf margin regulators, such as FveTCP5, FveTCP12, Fve-KNAT3 and FveSAW1, show a significantly lower expression in yuc4-2 leaves (Figure 7e). In particular, FveWOX9 and FveCKX3, homologs of the blade outgrowth repressor The Plant Journal, (2023), 115, 1428-1442 (Wang et al, 2022), were dramatically upregulated in yuc4-2 leaves. The expression of several flower development genes is reduced in yuc4-2 flowers, such as FvePIa, FvePIb, FveSEP3, FveAG and FveSEP4 (Figure 4f).…”

Identification and cloning of early senescence leaf mutant esl13 in rice (Oryza sativa L.)

“…In rice, higher chlorophyll content and leaf area index lead to higher yields (Chan, 2021). WUSCHELrelated homeobox family (Wang, 2017) and Teosinte branched1/Cincinnata/proliferating cell factor (Koyama et al, 2010) family play an important role in the regulation of leaf area. Chlorophyll is one of the essential substances of plant photosynthesis; and the higher the degree of senescence of rice leaf, the lower the chlorophyll content (Gu et al, 2016).…”

The STF/WOX1 MD is required for physical interaction with MtWOX9 and leaf blade outgrowth in Medicago truncatula

“…We previously reported that STF/LAM1/WOX1 physically interacts with WOX9 to antagonistically regulate the common targets CKXs in M. truncatula and N. sylvestris (Wang et al, 2022)…”